Well...for the first one...theoretically...once you experience intense pain, i mean really intense, sudden pain at one go, your brain goes into hyperdrive and produces endorphins and enkephalins, similar in chemical structure to morphine. This delyas the pain and sends you into a state of euphoria or sometimes shock. After that, the pain slowly hits, but something that intense...i doubt it will feel anything like pain. As for a yes or no answer...I would say yes, you may give up the will to live as your brain tries to search for the source of pain and starts to try and do something about it.
As for the second one, not very possible is it? A human bladder's capacity is like what? 800ml?
And as for the third? Poisoning for the 1st part, and cuts and scratches for the 2nd. Either way...you may have to go see a doctor...and maybe get an MC to recover...
